feat: add the TechLog asset multipart upload transport

Wires the whole Asset capability into the running application: the
multipart upload transport (the contract runtime can only express JSON
bodies), a single composition-root-owned CSRF provider shared between
the platform's credential collaborator (18 JSON operations) and the
upload transport (1 multipart operation), and Studio/StudioShell
exposure of the Asset gateway alongside the existing document gateway.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/features/tech-log/studio-asset-gateway.test.ts

@@ -67,6 +67,33 @@ test("lists assets through the canonical operation", async () => {
   assert.equal(calls[0]!.operationId, "listStudioAssets");
 });
 
+test("gets a single asset detail through the canonical operation", async () => {
+  const detail = {
+    asset: READY_ASSET,
+    usages: [
+      {
+        documentId: "22222222-2222-4222-8222-222222222222",
+        documentTitle: "Fetch Join과 Batch Fetch 비교",
+      },
+    ],
+    hasPublicationHistory: true,
+  };
+  const { calls, dependencies } = deps({
+    getStudioAsset: {
+      kind: "SUCCESS",
+      value: detail,
+      effect: "APPLIED_CONFIRMED",
+    },
+  });
+  const gateway = createHttpStudioAssetGateway(dependencies as never);
+
+  const result = await gateway.getAsset(READY_ASSET.id);
+
+  assert.equal(calls[0]!.operationId, "getStudioAsset");
+  assert.deepEqual(calls[0]!.input, { assetId: READY_ASSET.id });
+  assert.deepEqual(result, detail);
+});
+
 test("delegates upload to the transport with CSRF and idempotency headers", async () => {
   let received: Record<string, string> = {};
   const { dependencies } = deps({});